There has been a conventional technique for performing international connection by interconnecting mobile communication networks between different countries. FIG. 1 shows an example of an interconnection configuration between mobile communication networks via an international relay network. In the example of FIG. 1, each of an operator B network and an operator C network which are networks of operators (communication carriers) of a country (example: Japan) is connected to an international relay network, and also, an operator A network which is an operator network of another country (example: united states of America) is connected to the international relay network, so that international interconnection is performed.
The international relay network shown in FIG. 1 is an existing relay network based on the common channel signaling system, and the international relay network is connected to each operator network by a digital circuit (STM circuit).
An example of a call connection procedure via the international relay network is described with reference to FIG. 1. In this example, it is assumed that call connection is performed from a user A (UE-A (user apparatus-A)) of the operator A to a user B (UE-B). Also, it is assumed that the user B was originally a subscriber of the operator C, then, becomes a subscriber of the operator B by MNP (Mobile Number Portability). That is, the telephone number of the user B is a number managed in the operator C.
When the user A performs operation for originating a call to a user B incoming number at the UE-A, a connection request signal including the user B incoming number as a destination is transmitted (step 1). In the operator A network, the call origination is determined as a call origination to abroad, so that the connection request signal is transmitted to the international relay network. In the international relay network, since the user B incoming number is identified as a number of the operator C, the connection request signal is routed to the operator C network (step 2). In the operator C network, since the user B incoming number is identified as a number which is MNP-moved out to the operator B, the connection request signal is transferred to the operator B network, so that an incoming call arrives at the user B (UE-B) (step 3).